1. Field of the Invention
The present invention relates to a surface light source device and a display device using the same, and more particularly, to a surface light source device using a point light source and a display device using the same.
2. Description of the Background Art
Liquid crystal display devices, signboards, guide lights and the like are not spontaneous emissive display devices whose display part itself emits light. It is required for these non-spontaneous emissive display devices to have a surface light source device such as a backlight on the back face of the display part.
In a conventional surface light source device, a linear light source such as a cold cathode fluorescent tube, or a point light source such as a light emitting diode has been used as a light source disposed on a side surface of a light guide plate. When using the point light source, however, the light source is formed by arranging a plurality of light emitting diodes or the like in a row on the side surface of the light guide plate, and hence there may arise luminance non-uniformity between the region of the point light source, and the region near between the adjacent point light sources.
Japanese Patent Application Laid-Open No. 2001-14922 discloses a surface light source device. Specifically, to diminish the luminance non-uniformity of the light emitted from an opening part, concaves and convexes are provided on the whole of a light incident surface of a light guide plate, and light emitting diodes are fit into the concave portions. Further, reflecting members are disposed at the convex portions of the light incident surface of the light guide plate.
Nevertheless, even with the surface light source device employing the construction of the above-mentioned publication, the luminance is slightly higher in the region near point light source than the region near between adjacent point light sources because the point light sources are arranged discretely. The luminance difference may deteriorate the display quality in this surface light source device.